1. Field of the Invention
This invention relates to vacuum cleaners, particularly electric vacuum cleaners.
2. Description of the Prior Art
Electric vacuum cleaners have been highly developed in recent years, and many different models have been placed on the market. Vacuum cleaners for use in the home are generally of two types, often known as the cylinder type and the upright type. The cylinder type has a body, usually mounted on wheels, and containing an electric motor driven suction generating means such as a fan and a dust collection chamber in which usually dust collection bags are mounted to filter the sucked air. The air is sucked through a hose from a cleaning accessory such as a brush or a nozzle at the remote end of the hose. The hose has a coupling detachably connectable to a hose inlet leading to the dust collection chamber. Cleaning is conducted by moving the accessory over the surface to be cleaned.
The upright type differs in that the surface to be cleaned is located immediately beneath the body, so that a hose and an accessory are not required. Nevertheless the upright type is usually adaptable so as alternatively to suck air through a hose from a remote accessory. The upright type has the advantage that the body may also carry one or more brushes which are driven in rotation, and which contact the surface to be cleaned which is particularly advantageous when cleaning carpets.
Recently, in order to provide the same advantage in a cylinder type vacuum cleaner, there has been provided an accessory for mounting at the end of the hose, which itself has one or more rotating brushes for contacting the surface being cleaned. An electric motor mounted in the accessory rotates the brush or brushes. To supply electric power to this accessory, a cord or lead may be arranged inside the hose. The hose coupling engageable with the hose inlet and the hose inlet itself have a plug and socket arrangement for connecting this lead to electrical power source in the vacuum cleaner body. Safety requirements in some countries may not permit this arrangement. In that case, the electrical supply cord for the powered accessory must be located outside the hose, and a socket is provided on the vacuum cleaner body for insertion of a plug at one end of the cord. An example of the latter arrangement is shown in JP-A-58-49128, in which the power supply socket is arranged in the upper surface of the vacuum cleaner body.
This power supply cord to the accessory is conveniently attached by clips to the hose, so that it does not trail and become entangled with the vacuum cleaner or furniture etc. However, in order to allow flexing or rotation of the hose portion near the body, there must still be a free portion of cord which can form a loop which is liable to catch on the user or on furniture. If the hose is rotatable relative to the body, the cord becomes twisted around the hose. It is an object of the present invention, in a first aspect, to solve this first problem.
Increasing sophistication of the control of electric vacuum cleaners means that such vacuum cleaners commonly include printed circuit boards. The printed circuit board may carry a small electrical device, e.g. a switch, which is operated by the user through a control member, such as a switch button. There is a risk of damage to the delicate printed circuit board and the small devices which it carries, if excess force is applied by the user to the control member. For example if the control member is on the top of the vacuum cleaner, there is a tendency for users to employ their feet rather than their hands to operate the control member. In a second aspect, it is an object of the invention to provide a solution to this second problem.
The electric motor in the body of a vacuum cleaner is commonly cooled by the sucked air, the motor being on the exhaust side of the fan. The flow rate of sucked air varies in inverse dependence on the degree of vacuum being generated by the vacuum cleaner. When a high vacuum is being generated, the airflow may not be sufficient to cool the motor adequately, which then overheats. To prevent this, it is known to provide a bypass valve for admitting external air directly to the sucked air path, when a predetermined level of vacuum is experienced. In this way, a greater airflow over the motor is achieved. There is a problem that the bypass valve currently used admits insufficient additional air to cool the motor adequately. In a third aspect, it is an object of the invention to overcome this third problem.
If a vacuum cleaner is operated without a bag correctly located in the dust collection chamber, firstly any dust sucked will be readmitted to the room, and secondly dust may enter the electric motor. In an attempt to prevent this, it is known to design the mounting means for the dust bag in the dust collection chamber so that an incorrectly located bag usually prevents closure of the cover, which is opened to give access for installation or removal of a bag. This does not prevent closure of the cover when no bag is present in the dust collection chamber. In an attempt to solve this problem, one vacuum cleaner has been marketed by Miele in which a mount for the bag is pivotable and is biased into the position in which it obstructs closure of the cover, unless a bag is mounted on it. The weight of the bag overcomes the bias and pivots the mount into a position where the cover can be closed. The empty bag is light, so that the spring which biases the pivotable mount must have only a light force. This raises a difficulty of design and of maintenance. In a fourth aspect it is an object of the present invention to provide an improved arrangement for preventing operation when no dust bag is present.